The invention relates to valve assemblies and, more particularly, to displacement compressors using valve assemblies.
In displacement compressors that use valves, such as reciprocating piston compressors and the like, pressure actuated valves typically open and close once during each shaft revolution of the compressor. When the valve closes, it contacts the valve seat due to valve stiffness and/or pressure actuation. Depending upon compressor design and application, this contact can occur with a velocity that can be substantial, producing an impact between these components which also can be substantial.
While the valve is closed, it supports a pressure difference. The magnitude of this pressure difference depends upon the compression application.
The nominal maximum pressure difference supported by both suction and discharge valves in a reciprocating compressor is simply the difference between the discharge (high) and suction (low) pressures. If the valve is relatively thin, such as, for example, a reed type valve, then the valve in the closed position will deflect into the port somewhat due to the pressure difference. This deflection into the port will cause the portion of the valve contacting the valve seat to slide against the valve seat. This sliding motion produces wear of the material at the valve seat and the valve.
In many common applications, the valve deflection, and the sliding between valve and valve seat, is relatively small due to valve and valve seat design, compressor design, and/or applications with only low to moderate pressure differences. However, some applications may require the use of a thin reed type valve to support a high pressure difference. In these cases, the wear at the valve seat and valve may be significant, and this results in reduced useful life of the compressor and reduced performance due to leakage of compressed fluid between the valve and valve seat.
It is clear that the need remains for a reduction of the localized stresses that lead to material wear in the contact zone of the valve and valve seat, as well as a reduction of leakage.
It is therefore the primary object of the present invention to provide a valve assembly and compressor incorporating same which addresses these needs.
Other objects and advantages of the present invention will appear hereinbelow.